24-121
      
Checking voltage supply for oxygen sensor 
heating  
     
Test requirement:  
     
Fuse for oxygen sensor heating OK 
     
       Electrical Wiring Diagrams, Troubleshooting & 
Component Locations binder   
     
Fuel Pump (FP) OK, checking   Page 24
-
49
 . 
      Component location of harness connectors   
Overview of component locations, page   Page 
24
-5   
     
-  Disconnect 4-pin harness connector leading to 
respective oxygen sensor. 
    
-  Connect multimeter between terminal 1 and 2 for voltage 
measurement. 
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24-123
       If there is no voltage again:  
     
-  Check wire connection from terminal 1 to Fuel 
Pump (FP) relay via fuse for open circuit. 
     
       Electrical Wiring Diagrams, Troubleshooting & 
Component Locations binder         If voltage supply is OK:  
    
If there is no voltage:  -  Connect multimeter for voltage measurement as follows:Harness connector  
Terminal  
Measure 
to  
2 (Ground -GND- activation of Engine Control Module -
ECM-)  B+  
- Start engine.
 
Specification: approx. battery voltage, possibly fluctuating
-  Switch ignition off.
-  Connect VAG1598/31 test box at wiring harness to ECM, do not 
connect ECM   Page 24
-17
 . 
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